Gas Chromatography Flashcards
- technique used in analytical chemistry for separating and analyzing compounds in complex mixtures
- relies on the principle of differential partitioning of sample components between stationary phase and mobile phase
- high sensitivity, selectivity, and efficiency make it an indispensable tool for qualitative and quantitative analysis of organic compounds
Gas chromatography (GC)
principle of gas chromatography
partitioning equilibrium and interaction between phases
- inert gas, typically helium or nitrogen, that ocntinuously flows through the system
- acts like a moving platform, carrying the vaporized sample components through the column
mobile phase (carrier gas)
typically, what is the mobile phase (carrier gas)
helium or nitrogen
- thin layer of high-boiling liquid film coating the inner walls of a long, narrow column
- interacts with the sample components as they travel through the column
stationary phase
Two phases of the gas chromatography
- stationary phase
- mobile phase
what happens to the sample in gas chromatography
- vaporized and
- caried through a colum
strength of the interaction between sample and stationary phase is described by a value called the __ __
distribution constant (Kc)
compounds with stronger interactions with stationary phase take __ to elute from the column
longer
equilibrium between the concentrations of a compound in stationary phase and the mobile pase
- distribution constant or
- partition coefficient (Kc)
determines the movement of compounds through the column and thus enables the chromatographic separation
equilibrium constant
remove (an adsorbed substance) by washing with a solvent, especially in chromatography
elute
where is the stationary phase typically coated on
inner walls of column
the stationary phase is typically composed of materials like.. ?
silicon grease or wax
what affects separation efficiency by mobile phase
flow rate
Components of the Gas Chromatography
- stationary phase
- mobile phase
- injector
- detector
- data system
- where the sample is introduced into the system
- vaporizes the sample and injects it into the column
injector
- located at the end of the column, it detects separated sample components
- monitors the eluent leaving the column and provides a signal that correspons to the concentration of the sample components
detector
collects and analyzes detector output, providing information about sample components’ identities and concentrations
data system
in gas solid chromatography, the column consists of what?
- hollow tube
- packed with stationary phase
in gas-liquid chromatography, the column is what?
coated with thin layer of stationary phase
Two types of columns
- packed columns
- capillary columns
- filled with a solid support material, providing a large surface area for interactionb etween the sample components and the stationary phase
- suitable for separating less volatile compounds
packed columns
- have thin, coated layer on the inner walls, providing high separation efficiency and resolving power
- ideal for separating volatile compounds
capillary columns
transports the sample through the chromatographic system
carrier gas
carrier gas must be __, meaning they do not react with the sample or stationary phase, to ensure accurate analysis
inert
Types of inert gases
- helium
- hydrogen
- nitrogen
- most commonly used carrier gas due to its inertness, consistent flow rate, and broad applicability
- suitable for a wide range of analytical applications and compatible with various detectors
helium
- provides higher efficiency and faster analysis compared to helium due to its lower viscosity
- offers imporved separation of closely eluting compounds
- however, it is flammable and requires extra safety precautions
hydrogen
- inexpensive and readily available carrier gas option
- less efficient than helium and hydrogen but suitable for routine analyses
- often used when high-purity heloum or hydrogen is not available or cost is a concern
nitrogen
Techniques for injecting samples
- split injection
- splitless injection
- on-column injection
- divides the smaple into two portions: one directed into the column for analysis and the other vented out
- suitable for samples with a wide range of concentrations, preventing detector saturation
- enhances sensitivity for trace-level analytes
split injection
- introduces the entire sample into the column without splitting initially
- ideal for trace-level analysis by maximizing sample concentraton on the column
- ensures higher sensitivity but requires careful optimization to prevent detector overload
splitless injection
- directly introduces the sample onto the head of the chromatographic column
- suitable for thermally labile compoupnds or sample with a limited volume
- minimizes sample degradation and provide sharp peak shapes
on-column injection
- captures and processes chromatographic data, facilitating data analysis and interpretation
- converts detector signals into digital information and generates chromatograms, visual representations of analyte peaks
recorder or data system
Procedure of Gas Chromatography
- sample injection and vaporization
- separation in the column (retention time and peak analysis)
- detection and recording of results (interpretation of chromatograms )
where is the sample injected into
injection port
time taken for a compounds to travel from injection to detection
retention time
identify and quantify sample components based on their retention times and peak areas
peak analysis
provides insights into sample composition, purity, and concentration
interpretation of chromatograms
application of Gas chromatography sample
metabolomic profiling of human spermatozoa
